Face clutch



April 16, 1946. I E. WYILDHABER' 2,398,570

FACE CLUTCH Filed Sept; 1, 1942 5 Sheets-Sheet 1 4 1, i B g I] Zhmentor .m/vasr W/LDHHBER Gttorneg A m-i116, 1946.

E. WILDHABER FACE CLUTCH Eiled Sept. 1, 1942 5 Sheets-Sheet 3 Zmnentor ERA/E's r wan/man? E. WILDHABER FACE CLUTCH Filed Sept. 1, 1942 April 16, 1946.

5 Sheets-Sheet 5 Patented Apr. 16, 1946 FACE CLUTCH I y Ernest Wildhaber, Brighton, N. Y., assignor to Gleason Works, Rochester, N. Y;, acorporation g "of New York Application September 1, 1942, Serial No. 456,894

21 Claims.

The present invention relates to toothed face clutches and to methods of making such clutches. More particularly it relates to toothed face clutches which have helicoidal side tooth surfaces andwhich are adapted either to run in one direction only or to be disengaged automatically under excessive loads. 4

The present application is confined to the new clutch of this invention. The novel method of the invention is covered in my divisional application Serial No. 615,581 filed September 11, 1945.

One object of the invention is to provide a toothed face clutch in which the engaging members have mating side tooth surfaces, on one side of the teeth at least, that are helicoidal surfaces and in which the mating tooth surfaces of said members willengage with less than full length tooth contact so that undue concentration of the loads at the endsof the teeth maybe avoided,

when the clutch members are in engagement or are moving into and out of engagement. v

Other objects of the invention will be apparent hereinafter from the'specification and. from the recital of the appended claims.

The present invention may be applied to the manufacture of saw-tooth clutches as well as to the manufacture of clutches having opposite side tooth profiles that are symmetrically inclined to the clutch axis. In a clutch of the first-named type made according to the present invention, the teeth have helicoidal surfaces at one side only; the opposite sides of the teeth are surfaces of revolution. In a clutch of the second-named type made according to the present invention, both sides of the teeth have helicoidal surfaces.

In cutting or grinding the teeth of either type of clutch, a face mill cutter or an annular grinding wheel is preferably employed, and tooth surfaces are cut that are longitudinally curved, one side of a tooth space being longitudinally convex and the other side longitudinally concave. Moreover, in cutting or grinding eithertype ofclutch,

the two sides of a tooth space are preferably cut or ground in a single operation.

For cutting the helicoidal side of a tooth space of either type of clutch, the toolis rotated in engagement with the clutch blank while a simultaneous relative movement is produced between the tool and blank about and inthe direction of the blank axis. In a saw tooth type of clutch, the helicoidal side of a tooth space may be out first by feeding the tool into the blank while producing the described helical movement betweentool and blank about the blank axis. Then the 'tool may be allowed to dwell at full depth position long parallel to its axis.

may also be cut with 'a-cutter "side-cutting edges so cutting edges of the c enough to finish the opposite side of the tooth s'pace as a 'surface of revolution. Then the tool is withdrawn from engagement with the blank, and the blank indexed'tobring another tooth space into position for cutting. The tooth spaces ofa saw tooth clutch may also be finished by first feeding the tool intodepth in the direction of the clutch axis to finish one side of a tooth space as a surface of revolution, and then slowly withdrawingthe cutter or wheel outwardly while moving. thework about and inthe direction of its axis to produce a helicoidal tooth surface on the opposite side of the tooth space. In a clutch member having helicoidal surfaces on both sides of its teeth, one side of a tooth space is finished whilethe toolis being fed into depth, the opposite sidewhile' thetool is being withdrawn from depth. The work rotates continuously in the same direction and at a uniform velocity during both in and out feed. When the tooth spacehas been cut, the blank is indexed. I

In both types of clutches, the tooth spaces are 0 preferably cut to taper in depth from their outer to their inner ends. Only the tooth space bottoms need be tapered, however; the tops of the teeth may lie. in a plane perpendicular to the clutchaxis Because of the axial feed, the helicoidal sides of the .teeth are cut by the tips of the cutter blades. Since the. non-helicoidal sides of the teeth of a saw-tooth clutch are cut with sidecutting edges which lie atone side only of the cutter, a cutter may be used for cutting a sawtooth clutch member according to this invention which has all of its blades sharpened to cut on one side of a tooth slot only. This makes a very eff cient tool and speeds up the cutting operation. I The non-helicoidal sides of the teeth may be cylindrical surfaces and be cut with a cutter or grinding wheel having straight side-outing edges Preferably. however, such a clutchmember is cut edges are inclined to the tool axis. The cutter or wheel is then tilted so that its cutting edges will extend in the direction of the clutch axis. The'non-helicoidal sides of the clutch member having curved that the non-helicoidal sides of its teeth will-have-- side surfaces that are spherical or othercurved surfacesof revolution.

Where-both sides of the clutch teeth are helicoidal', cutting'of both'sides is done by the tiptter, one side being cut with a tool whose cutting.

during the in-feed, the other side during the outfeed.

Lengthwise mismatch of the non-helicoidal sides of the teeth of engaging clutch members may be obtained by using different diameter cutter to cut the mating tooth surfaces of the pair.

Lengthwise mismatch of the mating helicoidal tooth sides depends on the difference in the radii of the cutters, the tooth taper, and the radii of the tip cutting edges of the cutters as will be ex-. plained more fully hereinafter.

The invention may readily be practiced on a machine of conventional type for generating spiral bevel or hypoid gears with but slight modification of such a machine. In such a machine, means is already provided to rotate the work in time with depthwise feed thereof, and depthwise feed is effected by movement of a sliding base on which the work head is adjustably mounted. To use the machine for the purposes ofthe present invention, the work head may be set atzero so that the work axis will extend in the direction of the feed movement of thesliding base, Thus as thework rotates on its axis andis fed axially, the desired helicoidal movement between cutter and work will be obtained. It requires but a very slight modification in the work drive of'the machine to obtain the slow rotation, stoppage and reversal of the work that is desirable in order to cut efiiciently the helicoidal sides of the teeth.

Several different embodiments of the invention are illustrated in the accompanying drawings, in which:

Fig. 1 is a sectional view of a face clutch member made according to one embodimentof this invention, the section being taken in a mean plane, hereinafter referred to as the pitch plane, which is perpendicular to the clutch axis and in which the thickness of the teeth of the clutch member at any point in the length of the teeth equals the width of its tooth spaces;

Fig. 2 is a part elevational, part axial sectional view of this clutch member;

Fig. 3 is an elevational view showing this member in engagement with its mate, the two members constituting a saw tooth clutch made according to one embodiment of this invention;

.Figs. 4 and 5 are a fragmentary sectional view in a plane perpendicular to the cutter axisand a fragmentary elevationa1 view, respectively, of

a face mill cutter for cutting one member of a clutch according to this invention;

Fig. 6 is a mean circular section of one of the clutch members taken concentric with the clutch axis and on an enlarged scale, and illustrating diagrammatically one of the ways of cutting this clutch member; v Fig. 7 is a view similar to Fig. 6, but showing a clutchmember made according to a slight modification of the invention and illustrating diagrammatically the method of cutting the same;

Fig. 8 is an-enlarged fragmentary axial sectional view of the clutch member, showing the taper of its teeth and illustrating diagrammatically certain relationships between the cutter employed and the clutch'member;

Fig. 9 is a diagrammatic'view showing a blade of a cutter such as may be employed in cutting the clutch members of Figs. 1 to 3' inclusive, and

further illustrating diagrammatically the relationship between the cutter and the work required for cutting two sides of a tooth space of the clutch member simultaneously according to this invention;

Figs. 10 and 11 are diagrammatic view showedges of a pair of cutters, such as may be employed for'cutting the two members of a clutch according to this invention, will affect the lengthwise tooth bearing on the mating helicoidal sides of the clutch;

Fig. 13 is an enlarged fragmentary axial sectional view of one of these cutters taken adjacent the tip surface of the cutter, and further illustrating the relationship between the cutter and the work;

Fig. 14..is an enlarged elevational view of one of the clutch members, illustrating diagrammatically thenature of the helicoidal side surfaces of its teeth;

Figs. 15 and 16 are diagrammatic views taken in the planes perpendicular to the clutch axis, showing the cutting of mating helicoidal tooth surfaces of the two clutch members and how these tooth surfaces will have a lengthwise mismatch Or localized tooth bearing;

Figs. 17 and 18 illustrate diagrammaticall a preferred way of cutting or grinding one member of a saw-tooth clutch pair according to this invention;

Figs. 19 and 20 are corresponding views illustrating diagrammaticall the preferred way of cutting or grinding the other member of the clutch pair;

Fig. 21 is a diagrammatic view showing how the gear train employed in a standard gear cutting machine for rotating the work spindle may be modified in order to practice the present invention on that machine;

Fig. 22 is a view showing a detail of the mechanism illustrated in Fig. 21;

Fig. 23 is a velocity diagram, illustrating one way in which the machine ma be operated according to this invention to produce a saw-tooth clutch;

Figs. 24 and 25 are a sectional view in the pitch plane and a fragmentary elevational view, partly in axial section, respectively, of a clutch member made according to a further embodiment of this invention and having helicoidal surfaces on both sides of its teeth;

Fig. 26 is a mean circular section on an enlarged scale of this clutch member andillustrating diagrammatically the method of cutting the same;

Fig. 27 is a diagrammatic view further illustrating the relationship between the cutter and work in the cutting of this clutch member;-

Fig. 28 is a velocity diagram similar to Fig. 23, showing how the work spindle of the cutting machine is driven during cutting of the clutch member of Figs. 24 to 26;

Figs. 29' and 30 are fragmentary axial sectional views, showing a pair of cutters for cutting the mating members of a further modified form of clutch made according to this invention; and

Figs. 31 and 32 are views showing blades of two different modified forms of cutters.

In the drawings, 35 and 35 (Fig. 3) denote.

' respectively, the two members of a saw tooth the sides 38 ofthe teeth have straight profiles extending substantially parallel to the clutch axis 39 while the opposite sides 31 of the teeth are helicoidal surfaces-of constant lead. The tooth sides 38 are portions of surfaces of revolution and are preferably counterparts of the sidecutting surface of the cutter used to produce the clutch member. These surfaces 38 may be cylindrical surfaces, or conical surfaces or even surfaces of curved axial profile such as spherical surfaces.

The two members of the clutch pair have, respectively, of course, teeth of opposite hand. The sides 31 of the teeth of the member 35 are, for instance, longitudinally convex while the opposite sides' 38 are longitudinally concave. The mating sides 3'! and 38' of the other member 35 are longitudinally concave and longitudinally convex, respectively. In the illustrated embodiment of the invention the teeth of both members extend substantially radially of the clutch axis 39, that is, the median line 48 of a tooth is radial of the clutch axis 39.

For cutting the teeth of the clutch members 35 and 35 face mill cutters may be employed. A cutter of this type is shown in Figs. 4 and 5. It has a rotary head 40 and a plurality of cutting blades M which are arranged circularly about the axis 42 of the head and which have their cutting portions projecting beyond oneside face of the head in the general direction of the axis of the head. With such cutters it ispossible not only to cut the clutch members efficiently and at high speed but also to obtain a clutch in which the contacting toothsurfaces of the mating members havea desirable localization of lengthwise tooth contact. i

Fig. 6 illustrates.diagrammatically the cutting of the tooth surfaces of one clutch member, here the clutch member 35. The face-mill cutter employed in the cutting of the tooth surfaces 3'! and 38 of this member has cutting blades 55 whose opposite side edges 46 and 41 are of'straight profile and whose tip cutting edges 48 are rounded and preferably of circular shape. One blade 45 of the cutter is shown in full lines near the start of the cut when contact between the roundedtip cutting edges 48 of the cutter and the helicoidal side tooth surface 31, which is to be produced,

is at As the cutter rotates in engagement with the clutch blank to cut atooth space of the blank, a relative feed movement is effected between cutter and blank about the clutch axis and in the direction of the clutch axis. In the instance illustrated, the feed movement during cutting of the functioning part of a helicoidal side tooth surface consists of uniform rotation aboutthe clutch axis, which is preferably performed by the work, and of uniform feed along the clutch axis, also preferably performed by the 'work.

The dash line 54 denotes the path of travel of the center 50 of the rounded portion 48 of the cutter blades during the cutting operation. While the center is travelling from position 50 to position 50, the functioning portion of the side surface31 is out. In this part of the operation the tool follows a mean helix 52 in the desired side tooth surface and generates the desired helicoidal surface on the work. Throughout this movement, the finishing'cut along the whole of the helicoidal surface from top to bottom thereof is made by the same point 5 I' in the cutter profile.

After the tool has reached the position shown in dotted lines 45', the work rotation is slowed down, whereas the uniform axial feed motion may continue with the result that near the root the profile of the tooth side 31 is curved downwardly, as shown. A well rounded root portion 53 is thereby produced inthe bottom of the tooth space. This makes for increased strength.-- As the cutter approaches full depth position, the axial feed is also slowed down and, when the cutter reaches full depth position, the work stands still for a moment. It is during this part of the cycle that the tooth side 38 is finished and its shape is thus a complement of the shape of the side 41 of the cutting tool. 5|)" denotes the position" of the center of the tip portion of the cutter whenthe cutter is cutting at full depth. After the tool has attained full depth position, the ax'ialfeed is reversed and at the same time the work rotation is also reversed. This causes the tool tomove slightly away from the finished tooth side 38 so as to clear the same during its withdrawal movement. The axial feedin the reverse direction is performed at an increased rate and amounts to a rapid withdrawal after thecompleted cutting of a tooth space.

When the tool has cleared the blank, the blank is indexed. Then the cycle starts anew on the next tooth space with the tool being again fed depthwise and the work again rotating in the for-- ward direction.

Thecycle can, of course, also be performed in the opposite direction so that the tool is fed relatively into the blank slowly to first cut the side 33 and then, afterfull depth position has been reached and that side completed, the tool is fed slowly outwardly in the direction of the blank axis while the blank is rotated on its axis so that the tool will follow the desired helical path and produce the helicoidalside 31 of the tooth space. In either case,j the rotation about the work axis is sloweddown periodically to a moment of stand-still and preferably reversed for a short time.

To avoid completely any possibility of inter ference between the tip of a tooth of one clutch member and the rounded bottom of the tooth space' of the mating clutch member, the teeth of the clutch members may be slightly chamfered at their tips. Th tooth at the extreme right of Fig. 6 is shown so chamfered as indicated at 55. This chamfer may .be applied by hand. Chamfering can be completely avoided, however, by making the tip portion 43 of the cutting blades more rounded.

Theshapes of the clutch teeth may otherwise be, {varied within considerable limits. Thus a further embodiment of the invention is illustrated in Fig. '7. Here a clutch member 60 is shown whos teeth 6| have sides 62 of straight profile which are surfaces of revolution and opposite sides 63 which are helicoidal surfaces but so formed as to blend in with the rounded bottoms 64 of the tooth spaces. This tooth shape may be produced with a face mill cutter having utting blades 45, as already described, by rotat ing the cutter in engagement with theclutch blank while effecting a relative movement between the cutter and blank about and in the direction of the work axis as before, the in-feed and the work rotation being simply slowed down at the same moment and in a constant proportion to each other. in a position of full depth. 65 denotes the path of the center 50 of curvature of the rounded tip portion 48 of the tool during the cutting of the tooth space. The side 62 of the tooth space is The cutter blade 45 is shown cut, as in the previously described embodiment, during a slight dwell of the tool atfull depth position while the work is stationary.

-As-Wil1 be apparent, the width of the tooth spaces, or of th teeth, or both, mustdecrease from the outer to the inner ends thereof. In order to produce the desired taper in width of the tooth spaces where both sides of a tooth space are. produced in a single operation as is preferred, the tooth spaces are cut to taper in depth from their outer to their inner ends. The cutting path, that is, the path of the plane of the tip cutting edges of the cutter, is therefore inclined to a plane perpendicular to the clutch axis.

To obtain the desired taper, the cutting path must be so tipped that the line of intersection of the planes, which are tangent to the cutting edges that cut the opposite sides of a tooth space, will intersect the clutch axis 39. (Fig. 9) denotes a plane tangent to the rounded tip cutting edge 68 of the cutter at the point 5| in' this-cutting edge which finish cuts the central portion of the helicoidal sides of the clutch teeth. (2 denotesa plane tangent to the side cutting edge 41 of thecutter which cuts the opposite sides of the teeth. .These two planes intersect in a line 13, which appears as a point in Fig. 9. The cutting plane of the tipof the cutter should be so tilted with refer ce to a plane 14 perpendicular to the clutchaxis 39 and passing through point 5! that this line l3 will intersect the clutch axis in the same'point (Fig. 8) as said plane 14. In mathematical terms, with distance A equal to 5'|!5, which is the mean radius of the clutch, and 1) equal to the axial distance between points 5! and 13, then the inclination z of the cutting path to a plan perpendicular to the clutch axis can be determined from the equation:

for teeth extending in a generally radial direction, as illustrated.

1 This formula and cutting method apply broadly also to tools other than face mill'cutters as, for instance, single reciprocatory tools, broaches, etc. Ordinarily only the tooth space bottoms are tapered. The tops of the teeth may remain in a plane perpendicular to the clutch aXis as shown at 11 in Fig. 8.

It is possible to use face mill cutters whose straight side cutting edges 4'! lie in a cylindrical surface concentric with the cutter axis. Pref erably, however, cutters are used which. have conical cutting surfaces or broadly, cutting surfaces which have positive inclination to the cutter axis. In such cutters, the outside cutting edges have their smallest distance from the'cutter. axis at the tops of the blades and the inside cutting edges have their largest distance from the cutter axis at the tops of the blades. Such cutters are easier to relieve and, moreover, the blades do not require radial adjustment after sharpening. From the standpoint of grinding, rinding wheels whose active side surfaces are of positive inclination arestill more important on account of wheel life. I

Not all portions of the cutting profilesof a cutter are needed for cutting; a particular member of the clutch pair as willbe understood from Figs. -6 and 7. Oppositesides of the tooth spaces of one memberof the clutch may be cut, respectively, with the tip-cutting edges of the cutter and. with the side-cutting edges at one side of the cutter. Opposite sides of the tooth spaces of the other member of the clutch may be cut, respectively, with the tip-cutting edges and with the side-cutting edges at the opposite side of the cutter. Hence, if the whole cutting profile is embodied by sharp cutting edges, that is, if the cutter is provided with both inside and outside cutting blades, then the same cutter may be used for cutting both members of the clutch pair. It is preferable, however, to provide the cutter for cutting one clutch member with outside cutting blades only and the cutter for cutting the other clutch member with inside cutting blades only. In this way, the blades can be sharpened with the side and front rakes to obtain the keenest cutting edges on the parts of the profiles which are in operation during cutting of a particular member of the clutch pair.

The cutter 40 shown in Figs. 4 and 5'is of this character. Its blades 4| are all alike. All are inside cutting blades and contain keen inside cutting edges t3 and top cutting edges 44. These cutting edges are formed by sharpening the blades ii sothat the front faces 49 of the blades are positioned to give combined side rake (angle s, Fig. 4) and front rake (angle 71., Fig. 5). Thus a very efiicient cutter is obtained at the expense only of having somewhat blunt outside edges on theblades, but these edges do no cutting anyhow.

As has already been stated, it is desirable to have lengthwise mismatch between the contacting tooth surfaces of the mating clutch members so as to have localization of tooth bearing. Figs. 10 and 11 show diagrammatically a pair of cutters for producing a pair of mating clutch members according to this invention Whose contacting tooth surfaces will engage with less than full length tooth contact. The cutter (Fig. 10) for cutting one clutch member has a straight outside profile 8| positively inclined to the cutter axis 82, a straight inside profile 83 also positively inclined to the cutter axis 82, and a substantially circular tip-cutting profile 84 which joins the two straight side profiles. The inside profile 83 is more inclined tojthe cutter axis 82 than is the outside profile 8!. The cutter (Fig. 11) for cutting the other clutch member has an outside cutting profile 9i positively inclined to the axis 82 of the cutter, an inside cutting profile 93 also positively inclined to the axis 92 but more inclined than the profile 9|, and a curved tip cutting profile 94 joining the profiles 9| and 93. For most efiicient cutting action, the blades of the cutter 86, which cuts one member of the pair, may be sharpened toout only with the portions 81 and 84 of their profiles While the blades of the cutter 9a, which cuts the other member of the pair, may be sharpened to out only with the portions 93 and 94 of their profiles.

Lengthwise mismatch of the contacting straight profiled sides of the teeth of mating clutch members is obtained by using a cutter 89 for cutting one clutch member having a normal radius 85-436 for its outside cutting surface at mean point 35 which is larger than the normal radius 95-96 of the inside cutting profile of the other cutter 9!] at mean point 95.

Lengthwise mismatch of the contacting helicoidal side surfaces of the mating clutch members depends on the relative length of the normal radii 8l83 (Fig. 10) and -9l98 (Fig. 11) of the tip cutting edges of the two cutters, where points 31 and 9? are, respectively, the points which finish the contacting mean portions of said heli- The last named factor will now be considered further. I00 and III! (Fig. 12) denote two face mill cutters which are adapted to cut, respectively, the two meshing members of aface clutch constructed according to this invention. The

axes of these two cutters are at I02 and H2, re-

spectively. The cutter I00 has outside cutting edges I03 and rounded tip cutting edges I04. The cutter IIO has inside cutting edges III and rounded tip cutting edges H4. The center of the rounded tip cutting portion I04 of a blade of the cutter I00 is at I05 and the center of the rounded tip cutting portion II4 of a blade of the cutter II 0 is at II5. In the position shown in Fig. 12, the two cutters are shown with the rounded cutting surfaces of two of their blades in contact with one another at the points I01 and H1, respectively. v Thesetwo points are the points in the rounded tip surfaces of the blades, which I finish, respectively, the mean portions of the helicoidal contacting sides of the engaging clutch members. r

In the instance illustrated in Fig. 12, the normal radii I I8 of the two cutters at common point I01, ,I I1 are equal. Despite this, however, length;

wisemismatch will be obtained between the contacting helicoidal tooth surfaces of the engaging clutch members when in mesh. This will now be demonstrated. I v I will be apparent from Fig. 14, inany clutch member I20 whose teeth I2I have helicoidal side tooth surfaces I22 of generally radial profile, the helicoidal side surfaces of the teeth contain helices whose inclination to the clutch axis II9 varies from one end of the tooth surface to the other. This is because the lead angles of the helices vary with the radial distance fromthe clutch axis. Thus, as shown in Fig. 14, the helices I24;and I26 at opposite ends of a helicoidal tooth surface I22 of the clutch member are inclined to one another and have different inclinations to the clutch axis. ,As will be noted, these helices appear as substantially straight lines in the zone of the tooth surface itself.

Letus assume for the moment that, instead of having a clutch member whose teeth have longitudinally curved side surfaces cut by a too1having cutting edges travelling in a longitudinally curved pathabout a fixed axis, we have a clutch member whose teeth have no lengthwise curvadrawing plane of Fig. 12 and having a profile I04 or I I4 centered at I05 or ll5,.respectively.

Fig. 13 is a fragmentary axial sectional view through a blade of the cutter I00 on an enlarged scale and may be'considered also as a fragmentary view of the cylindrical surface which would be present if the tool were a rectilinearly reciprocating tool. In cutting a helicoidal side surface of a straight toothed clutchmember with such a cylindrical cutting surface, the points of contact between the cutting surface of the tool and the helicoidal tooth side will change a the tool moves along the tooth surface from one end thereof to the other. Thus the cutting surface "I04 of the tool will contact with the helix I24 at the inner end of the tooth surface in point 121 while the cutting surface I04 will contactwith the helix I25 lying at a mean point in the length of the tooth surfac in point I01 and the cutting surface I04 will contact with the helix I26 lying at the outer end of the tooth surface in a point I28. i

The helix I24 at the inner end of the tooth surface will intersect a plane I29 perpendicular to the axis I02 of'the-cutter and containing the point I01 ina point I30 which lies at the right of thepoint I01 and whose distance from the point I01 increases with increasing distance of the helix I24 from the mean helix I25. Likewise the helix-I26 at the extreme radial'distance from the axis I23 of the clutch will intersect the plane I29 in a point to the right of point I01. It will be seen, therefore,"that there is a difference between the, lengthwise sectional profile 'of the cutting surface I04 and the lengthwise sectional profile of the helicoidal tooth surface produced thereby. It will further be seen that this departureis independent of the lengthwise shape of the cutting surface for all practical purposes. That is; at any given radial distance from the clutch axis. either side, of a mean point in the tooth length, the separation'of'the lengthwise cutting profile and of the lengthwise tooth profile is the same for a tool movingyin a straight path as it i for a tool moving in a longitudinally curved path.

Fig. 16 is a sectional view in a plane corresponding to the plane I29 ofFig. 13,,showingthe cut.. ting of a helicoidal side tooth surface I 22 of clutch member I20. I06 denotes oneoftheblades of the cutter and I36 is the path taken by a point in the tip cutting edge of the blade as the cutter rotates about its axis I02., The convex surface ,cut on the, helicoidal tooth side I22 is seen to be more curved than the concave cutting surface lI36 traced by the tip cutting, edge of the: cutter 00. w 1 r i Fig. 15 is a section similar to that of Fig. 16, showing the cutting of a helic0idalsurfacel32 of the clutch member I which is to engage with the clutch member I20. Points H1, in the tip cutting edges of the blades II6 of the cutter H0 will trace a, path I35-as those blades revolve about the axis I I2 of the cutter, which willl e more curved than the concave helicoidal side surface I32 produced by thoseblades; It willbe seen, therefore, that although the tip cutting surfaces I04 and H4 of the two cutters I00 and H0 have thesarne normal radii, IIB, the two helicoidal surfaces I22 and I32 produced, respectively, by these cutting surfaces will not match each other along-their whole length but will contact with a localized tooth bearing as is desired;

Figs. 15 and 16 show the curvature of the sur faces much exaggerated and this curvature is usuallyouite; slight and is hardly to be noticed in a view such as Fig. 14. a y

. It is seen from the foregoing that the produced mismatch increases with increasing profile radius of the tip cutting, edge of the cutters and also with increasing length of face of the clutch teeth; It is reduced with increasing inclination i of the cutting plane to a plane perpendicular to the clutch axis, and it can be'controlled readily by the cutter design. For instance, to reduce the length of tooth bearing on the straight profiled side I23 (Fig. 14) of a clutch tooth I2I and increase the length of tooth bearingon the helicoidalside" I22; change the relative diameters of the cutters employed-for cut ting the two members of the clutch,'namely, re duce the diameter of the cutter H as compared with the diameter of the cutter I00. This aim would be attained if the cutter I I0 had its axis in position H2 (Fig. 12) insteadof at H2; To increase the length of tooth bearing on "both sides I22 and I23 of the clutch teeth, increase the inclination of the inside cutting edges I II of the cutter H0 or decrease the inclination of the outside cutting edges I03 of the cutter I00. A decrease of the outside blad angle of the cutter I00 would result if the axis of this cutter were, for instance, at I02 (Fig. 12) instead of at I02.

Complete control of the amount of lengthwise tooth contact between the two members of a clutch can, therefore, be obtained by combining control of the normal radii of the two cutters with control of inclination of the direction of the cuting path and control of the radii of the tip cutting surfaces. The cutter specificationsmay be computed mathematically to give a desired amount of localization of bearing on both sides of the clutch teeth or they may be arrived at experimentally. Cutter diameter changes, in particular, are very easily made in practice;

Figs. 17 and 18 further'illustrate the preferred Way of cutting or grinding the clutch member I20 whereas Figs. 19 and 20 illustrate the preferred way of producing the clutch member I80 which engages therewith.

The cutters 80 and 00; respectively (Figs. and 11) may be used for cutting'these two clutch members. The cutter 80 has, as already described, outside cutting edges 81 or positive in clination to the cutter axis 82 and the cutter 90 inside cutting edges 9| also of positive inclination to its axis 92. The cutters are shown in positions of full depth engagement with the clutch members I and I80, respectively, and theyare, so tilted that the surface normals 'l8I and I9I,re-

spectively, at mean points 85 and 95, respectively,

lie in planes I83 and I9 3, respectively, perpendicular to the clutch axis H9. -'I'he cutter 8 0, which cuts with its outside cutting edges 8 I, is tilted into the work but it clears the clutch tooth zone opposite to that where it is cuttingbecause of the taperin depth of the teeth and tooth spaces. It is' often necessary, however, to observe a relationship between the tooth number and the cutter diameter so that the cutter may dip into a tooth space in the tooth zone opposite where it is cutting without touchin the final finished sides of the tooth space. In the plan view of Fig."18, the cutter axis 82 appears offset from the clutch axis H9 on the side opposite the point 85 where the cutter is cutting. I84 denotes the path of a mean point in the cutting surface during a revolution of thecutter.

Cutter 90, which cuts with its inside cutting edges 9|, is tilted away from the work I80. In the plan view of Fig. 20, the cutter axis- 92' appears to be offset from the clutch axis II9 on the same side as the mean contact point 95. I04 denotes the path of a mean point in the cutting surface during a revolution of the cutter.

As the cutter rotates on its axis in the cutting of either clutch member I20 or I80, the work is 'rotated on its axis H9 and is moved lengthwise of its axis to cut the helicoi'dal sides or the teeth, while the non-helicoidal sides are cut with the cutter at full depth position, as previously described.

'As already stated, saw-tooth clutch members constructed according to this invention may be attests cut on standard spiral bevel gear cutting machines with slight modification of such machines. Feed in the direction of the work axis is obtained on such machines by setting the work so that its axisextends in the direction of the feed movement of the sliding base on which the work head is mounted in such a machine. The required rotary motion of the work, which comprises uniform rotation, stoppage, and reversal all during the cut, can be secured by various means, one embodiment of which is illustrated in Figs. 21 and 22.

This work rotating means is so constructed as to drive the work at a uniform velocity during part of each cutting cycle and to impart periodically to the work an added rotary motion at a varying velocity to effect stoppage, reversal of the work, and indexing. The uniform motion is produced by bevel'gears 200 and MI which are driven from'any suitable source of power. The nonuniform motion is a Geneva motion in the illustrated instance produced by the actuating member 202 and the Geneva wheel 203.

The gear 20I is secured to a shaft 204 to which is also secured a bevel gear 206 that forms one of a set of differential gears comprising the bevel side gears 208 and 201 and the planetary bevel gear 208. The last named gear is secured to a stud 209 which is rotatably mounted in the differential housing 205. The side gear 201 is secured to a shaft 2 which is aligned with the shaft 204 and the housing 205 itself is journaled concentric with the aligned shafts 204 and 2| l. The shaft 2 is geared to the work spindle 2| 2 by the change gears 2I3, 2l4, 2I5 and 2I6, the

shaft 2 I1, the worm 2 I8 and the worm-wheel 2| 9. The latter is secured to the work spindle 2I2 which carries the clutch member to be cut.

The actuating member 202 of the Geneva mechanism is secured to a shaft 220 which is driven from the shaft 204 through change gears 2 I I and 222 at a 1 to 2 ratio in the instance shown so that shaft 220 may make one revolution per tooth space of the clutch member being cut and the shaft 204 will make two revolutions per tooth space of the clutch member being cut. The actuating member 202 carries a pin or roller 224 which is adapted to engage in a slot 225 of the Geneva wheel 203 to drive the Geneva wheel.

During cuttingof' the helicoidal side surfaces of the teeth, the housing 205 is stationary and the work is driven at a uniform velocity. During this part of the operation, the shaft 204 turns in the direction 226 causing the shaft 2| I to turn in the opposite direction 221. Periodically, however, the pin 224 engages the slot 225 of the Geneva wheel 203 to turn the housing 205, This tends to turn shaft 2 in the direction 226 which is op posed to the direction 221. The resultant combined motion is transmitted to the work spindle 2I2 through the change gears 2I3, 2I4, 2I5, and 2I6, the shaft 2I1, the worm 2I8 and the wormwheel 2 I 9. Thus, periodically an added motion at a varying velocity is imparted to the work spin- 116 to slow the work spindle rotation up and to stop it, and reverse it, thereby to obtain the movement of the work required for cutting the tooth spaces.

A velocity diagram of the work rotation is shown in Fig. 23. The abscissa denotes the angle of rotation of the shaft 220. Distance 230 represents a tooth cycle. The ordinate 23'I at any point 232 in the rotation of the shaft 220 is a measure of the speed of rotation of the work spindle 2 I2 or of shaft 2 in comparison with the speed of rotation of the shaft 220 at that moment. The

asesmo I I 7 velocity of rotation of the work spindle stays constant up to point 233 when the Geneva, motion becomes effective. Then the rotation slows down. It is reversed at point 234; reaches maximum speed in, reverse at point 235; then slows down gradually to point 236 where forward rotation begins again. Forward speed quickly picks up until point 231 is reached where the effect of the Geneva motion ceases and uniform rotation begins again in the cutting of the side of a new tooth space. The total turning motion of the shaft 2| l per tooth cycle is two turns less /2 turn which is subtracted by the Geneva motion, that is, it is 1 turns in the instance shown. The index gears 2|3, 2I4, 215 and 2l5 have then to be so chosen that 1 /2 turns of .theshaft 2| I are reduced to turns of the work spindle, where ndenotes the number of teeth in the clutch member to be cut.

Figs. 21 and 22 illustrate only one form of mechanism for effecting the desired motion of the work. There are other Ways in which this same result may be achieved, as, for instance, by using cams to produce the varying rotation.

'Figs. 24 to 26 inclusive illustrate a further em bodiment of clutch made according to this invention. The clutch member 240 here illustrated has teeth 24l with helicoidal surfaces on both sides 242 and 243. The opposite side surfaces of the teeth are helicoids of the same lead but opposite hand. Both sides of a tooth space maybe produced in the same operation by slightly inclining the cutting direction, that is, by cutting the tooth spaces to taper in depth. Thus the bottoms 245 of the tooth spaces will be inclined to the pitch plane, see Fig. 25.

Inclination angle i of the cutting direction to pitch plane or any plane of rotation perpendicular to the clutch axis 246 can readily be determined, as indicated diagrammatically in. Fig. 27.

The tangents 250 and-25l at mean finishing points 252 and 253, respectively, in the tip cutting profile of a blade 255 of the face-mill cutter used to cut the clutch member are firstdrawn. Then a circle 256 isdrawn about a point 251. The point 257- is midway between the points 252 and 253, and the circle 256 is so drawn as to pass through the intersection point 259 of the tangents 250 and 25L Line 258 is then drawn through points 252, 251 and 253. Then the mean clutch radius A is plotted on the line 258 from point 251 to point 246'. The line 260 is then drawn from point 246' tangent to circle 255 at point 259. The angler is the angle included between the lines 258 and 260. In mathematical terms, with b=distance 25l-259,

form in-feed to full depth, reversal, and uniform out-feed while the work; rotationgoes on uni,-

formly in the same direction. The centerof the cutting profile then moves from position 262 to position 262' during the uniform in-feed, thence toposition 262" during reversal and acceleration and from 262" to 252", during the uniform out-feed. A tooth space is then completed. gAS the axial feed. motion is slowed down,,reversed, and broughtup to full speed again, the clutch is indexed and the cycle begins anew on the next toth space with the center of the effective cutting surface of thecutter at position 2625:. The cutting tool is, shown in full line position at the beginning of thecut on one tooth space and in dotted lines'at nearly full depth position in the cutting of the next tooth space.

In order to achieve indexing from tooth space to tooth space, the work may go on rotating at a uniform rate, but its rotation is preferably sped up so that thedistance 262"'262ct is covered at a faster rate and the non-cutting time is reduced to a minimum. A mechanism similar to that illustrated in Fig. 21 can be provided to achieve the speed-up. In this case, an idler may be used between the change gears 22! and 222 so that'the shafts 220 and 204 will turn in the same direction. The Geneva motion is then applied .in the same direction'to the shaft 21! as is the uniform rotationof the shaft 204. For the cutting of a clutclfmember such as shown in Figs. 24 to 26 inclusive, the turning ratio of shafts 254 and 220 may be made 1 to 1 so that each of said shafts, performs one revolution per tooth cycle. l

A velocity diagram of the operation of cutting the clutch member 240 is then illustrated diagrammatically in Fig. 28. 210 denotes the tooth cycle. The abscissa denotes the angle of rotation of the shaft 220. The ordinate is a measure of the turning speed of the 1 work spindle.- The velocity of rotation of the work is uniform from the point 262to the point 262" during the cutting of a tooth space. Then it is accelerated and deoelerated again between the point 262"" and the point 263a when no cutting is going on. Then the uniform rotation begins'again for the cutting of the next tooth space.

As has already been indicated, the invention is not limited to the cuttingofclutohf members with tools of the types previously described.

Thus, in the cutting of saw-tooth clutches, tools of various profile shapes may be used. Figs. 29 and 30, show a pair of cutters having curved sidecutting edges for cutting saw-tooth clutch members made according to a further embodiment of the invention. The two cutters are designated lfilland l'lll, respectively. The axes of these two cutters are at I6! and I'll, respectively. The cutter I60 has a curved outside cutting profile 32 which is a circular are centered at point I63 on the cutter axis IBI. The cutter I10 has a curved inside cutting profile I12 whichis a circular are centered at I13 on the cutter axis l H. I64 and l'l4, respec tively', are the normals at the mean points H55 and "5, respectively, in the side-cutting edges of the two cutters which correspond to matching points of the contacting non-helicoidal sides of the two engaging clutch members. Mismatch on these sides of the clutch teethis obtained when the normal radius 163- l65 is made larger than the normal radius ll3 H5. Withthe described construction, the outside cutting surface having the profile 162 is part of a spherical surface and the inside cutfaces produced by these cutters on one side of the teeth of the mating clutch members. The opposite helicoidal sides of the teeth of these clutch members are produced as before by curved tip cutting edges I66 and I16, respectively, which are circular arcs centered at I61 and I'll, respectively. The points I68 and I18, respectively, in

these curved tip-cutting surfaces are the points which finish cut the mean portions of the helicoidal sides of the clutch teeth.

As has also been stated, the radii of the edges for cutting the helicoidal sides of the clutch teeth may be varied too. In Fig. 31, I have shown a blade I40 which has a much larger tip-cutting edge radius than any of the blades of the cutters previously described. Here the tip-cutting edge is denoted at I4I. Its center of curvature is at I42 while its curvature radius is denoted at I43. I45 in Fig. 32 designates a blade having a still larger radius of cutting edge for cutting the helicoidal sides of clutch teeth. The curved cutting edge is denoted at I46, its radius at I41, and its center at I48. In the case illustrated in Fig. 32, the curved cutting edge I46 constitutes the whole of one side and the tip profile of the blade.

Large radii of profile curvatures-such as I43 and I 41, for cutting helicoidal sides of a clutch tooth are desirable in order to obtain smooth finish and also for reducing the number of cuts required. Their use is, however, limited to the cutting of clutch members having moderate tooth face. length. The line of contactbetween the curved cutting surface and the helicoid produced thereby is inclined to the direction of cut and its inclination increases with increased profile radius. A line of contact between the cutting surface of the blade I45 and the helicoidal surface produced thereby at a mean feed position during cutting is shown at I5Il-in Fig. 8. This line of contact is seen to be more inclined to a plane of rotation perpendicular to the axis 39 of the clutch memher than is the cutting plane I3 or a plane I3 parallel thereto. It is obvious that if the radius of the curved cutting surface, which produces the helicoidal toothed sides, were increased in such way as to exaggerate the inclination of the line I50, not enough of the helicoid' would be formed at the inside ends of the clutch teeth. Hence, as stated above, the curvature radius of the cutting edges for producing the helicoidal sides of the clutch teeth is limited by the face width of the clutch member to be out.

In generalit may be'said that while the invention has been described in connectionwith certain particular embodiments thereof, it will be understood that it is capable of still further modification and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to whichthe invention pertains and as may be applied to the essential features hereinbefore set forth and. as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. A toothed face clutch member having teeth, each of which extends in a general radial direction from the periphery of said member toward its axis and each of which is curved longitudinally from its outer to its inner end, each of said teeth having a helicoidal sidetooth surface on at least one side.

2. A toothed face clutch member having teeth curved longitudinally across its face which taper in depth from their outer to their inner ends and which have helicoidal side tooth surfaces.

3. A toothed face clutch member having teeth curved longitudinally across its face which taper in depth from their outer to their inner ends and which have plane top surfaces and helicoidal side tooth surfaces.

4. A pair of engaging toothed face clutch members whose teeth have contacting side tooth surfaces which are helicoidal surfaces and which have less than full length contact.

5. A pair of engaging toothed face clutch members having teeth curved longitudinall across its face which taper in depth from end to to end and have contacting side tooth surfaces which are helicoidal surfaces and which have less than full length contact.

6. A toothed face clutch member having teeth curved longitudinally across its face, opposite sides of which are surfaces of revolution and helicoidal surfaces, respectively, one side of each tooth being longitudinally concave and the opposite side longitudinally convex.

7. A toothed face clutch member having teeth curved longitudinally across its face whose opposite side surfaces are portions of helicoidal surfaces, one side of each tooth bein longitudinally concave and the opposite side longitudinally convex.

8. A toothed face clutch member having teeth curved longitudinally across its face, opposite sides of the teeth being longitudinally concave and longitudinally convex, respectivel one side of each tooth being a surface of revolution'oi straight profile extending in the direction of the axis of the clutch member, and the opposite side of each tooth being a helicoidal tooth surface of constant lead.

9. A toothed face clutch member having teeth curved longitudinally across its face, opposite sides of which are longitudinally concave and longitudinally convex, respectively, one side of each tooth being a conical surface of revolution and the opposite side of each tooth being a helicoidal surface of constant lead.

10. A toothed face clutch member having teeth curved longitudinally across its face, opposite sides of which are longitudinally concave and longitudinally convex, respectively, one side of each tooth being a spherical surface of revolution and the opposite side of each tooth being a helicoidal surface of constant lead.

11. A toothed face clutch member having teeth curved longitudinally across its face, opposite sides of which are longitudinally concave and longitudinally convex, respectively, one side of each tooth being a cylindrical surface and the opposite side of each tooth being a helicoidal surface of constant lead;

12. A toothed face clutch member having teeth curved longitudinally across its face, opposite sides of each tooth being a helicoidal surface and a surface of revolution, respectively, the axis of the last named surface being inclined to the axis of the clutch member.

13. A pair of toothed face clutch members, one of which has opposite side tooth surfaces that are respectively longitudinally concave helicoidal surfaces and longitudinally convex surfaces of revolution, and the other of which has opposite s de tooth surfaces that are respectively longitudinally convex helicoidal surfaces and longitudinally concave surfaces of'revolution, the contacting tooth surfaces of the two membershaving different radii of lengthwise tooth curvature so that the engaging tooth surfaces have less than full length tooth contact.

14. A pair of toothed face clutch members whose opposite side tooth surfaces are helical surfaces which are longitudinally curved, contacting tooth surfaces of the two clutch members having different lengthwise curvatures so that the contacting tooth surfaces have less than full length tooth engagement.

15. A toothed face clutch member having teeth whose side surfaces are longitudinally curved helical surfaces whose axes are coaxial with the axis of the clutch member.

16. A toothed face clutch member having teeth curved longitudinally across it face whose opposite sides are surfaces of revolution and helicoidal surfaces, respectively.

17. A toothed face clutch member having teeth whose opposite side surfaces are helicoidal surfaces of the same lead but opposite hand.

18. A toothed face clutch member having tooth spaces tapering in depth from end to end, the

tooth surface at one side, at least, of each tooth space being a helicoidal surface.

19. A toothed face clutch member having tooth spaces tapering in depth from end to end, the tooth surfaces of both sides of each tooth space being helicoidal surfaces.

20. A toothed face clutch member having teeth and tooth spaces which taperin depth from end to end, one side of each tooth being of straight profile parallel to the axis of the clutch member and the other side of each tooth being a helicoidal surface coaxial with the clutch member.

21. A pair of toothed face clutch members having teeth and tooth spaces which taper in depth from end to end, mating side surfaces of the teeth of said members having less than full length tooth contact and being, at one side of the teeth at least, helicoidal surfaces coaxial with said members.

ERNEST WILDHABER. 

